HELP! What to do about warped MDF . . .

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Forum topic by lightweightladylefty posted 02-05-2010 06:36 PM 12546 views 0 times favorited 12 replies Add to Favorites Watch
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3241 posts in 3734 days

02-05-2010 06:36 PM

Topic tags/keywords: question mdf workbench outfeed table

I’m in the process of recycling lab cabinets from university surplus into a workbench that will be the outfeed table for my saw. This is a very low budget bench and I’d like to keep it that way.

I purchased 1-1/8” MDF for the top ($3.00 a sheet). The one that I cut for this bench is rather dirty on one side and it is warped. In the picture below, I can eliminate the warp by clamping it with the wrong side up since I can then pull the edges down. However, I don’t know how to eliminate it when I turn it over (with the clean side up) and the hump is in the middle. (The top is approximately 32” x 57”.)

I had thoughts of leaving it clamped upside down and covering it with a damp towel, letting it all dry out again, and unclamping it. Has anyone ever tried that, or would I ruin the MDF?

Because there are drawers directly below the top (as seen in the photo below), I don’t know what options I would have to force the center down.

I thought about using curved cauls across the top and clamping the edges but I don’t know if I can get enough pressure on the center to make it flat. And would it stay flat without tearing out screws if I attached it from the underside (inside the drawers)? (I would have to attach a bracket to the underside of the top and then drive the screws into the dividers between the drawers.) Or should I just drive screws through from the top down and countersink them?

Does anyone have ideas? I’m open to any suggestions.

-- Jesus is the ONLY reason for ANY season.

12 replies so far

View dennis mitchell's profile

dennis mitchell

3994 posts in 4336 days

#1 posted 02-05-2010 06:58 PM

Sand the dirty side clean. Gravity should fix the warp if you let it set a few months.

View Rj's profile


1047 posts in 3653 days

#2 posted 02-05-2010 07:11 PM

I would counter sink the screws and drive them into cabinets were its solid not above the drawers were the frame might warp . Then cover the top and sides with a high presure laminate like a formica type product.It will look great and is super easy to clean up glue dirt etc.

-- Rj's Woodworks,San Jose & Weed Ca,

View lightweightladylefty's profile


3241 posts in 3734 days

#3 posted 02-06-2010 12:50 AM

Dennis and RJ, thanks for your input.

Dennis, we already attempted the sanding but the discoloration is deep enough that it would require too much to keep the surface level. I’ve had the top clamped in this position for a few weeks now (thinking that gravity would fix the warp), and as soon as I take the clamps off, it springs right back up so I’m not certain how long it would take to level out just sitting there or if it ever would get flat.

RJ, the laminate idea sounds like a possibility. Now, if I can find some locally that doesn’t cost more than the whole cabinet (or without driving 50+ miles—we’re in the middle of no where), that should be a good fix. I’ll check around.

-- Jesus is the ONLY reason for ANY season.

View DaveA's profile


46 posts in 3103 days

#4 posted 02-06-2010 02:31 AM

If it were mine I’d use small angle brackets off the rails and screw into it from the bottom. Or, I would countersink screws through the top into the rails. I think pulling the hump down is an easier proposition than pulling the curved ends down.

-- Dave - Milwaukee

View a1Jim's profile


117113 posts in 3599 days

#5 posted 02-06-2010 06:43 AM

Replace it ?

-- wood crafting & woodworking classes

View rsmith71's profile


269 posts in 3064 days

#6 posted 02-06-2010 07:08 AM

In my experience, with MDF it’s actually easier to pull the ends down. I would run glue beads around where cab touches the MDF, screw it down from top side with the bow pointing down, putty or bondo over screws and cover with laminate and band edges with hardwood. The laminate will hold up longer than bare MDF.

-- Robert - Haven Wood Crafts

View Enthalpy's profile


44 posts in 3063 days

#7 posted 02-06-2010 02:05 PM

I agree with A1Jim…MDF is cheap…

View Sawkerf's profile


1730 posts in 3090 days

#8 posted 02-06-2010 05:43 PM

If it were me, I would get a new piece of MDF (it’s cheap), band the edges with solid wood, apply a couple of coats of finish to the top, bottom, and banding; and attach the top with figure-eights.

That’s a nice looking cabinet and trying to beat the salvaged MDF into submission might tweak the cabinet in ways you won’t like.

Save the salvaged MDF for something where appearance doesn’t matter.

-- Adversity doesn't build reveals it.

View dennis mitchell's profile

dennis mitchell

3994 posts in 4336 days

#9 posted 02-06-2010 06:31 PM

You might be able to stain it dark.

View lightweightladylefty's profile


3241 posts in 3734 days

#10 posted 02-07-2010 04:19 AM

Thanks guys for all your comments.

Sawkerf, I do plan to band and reinforce the edges with oak. I like the idea of the figure eights, but I’m just not sure if it is a possibilty with the way I plan to reinforce the edges.

(Cheap is a relative term. All our oak trees are dying so the nicer ones we have milled into lumber which costs us about 10 cents a board foot. To get another piece of 1-1/8” MDF, I would have to travel 50+ miles or pay $75 to have it delivered, and it wouldn’t be the $3.00 I paid for this piece [probably more like $30.00], so it would end up costing me more than the bench.) ;-(

I’ll post the bench if I ever get it finished.

-- Jesus is the ONLY reason for ANY season.

View Sawkerf's profile


1730 posts in 3090 days

#11 posted 02-07-2010 06:26 AM

Yeah, with those obstacles, I would be inclined to use what you have, too – lol

I often use my figure eights so the top attachment is on the inside of the cabinet frame. I attach the figure eights to the cabinet frame, lay the top on my bench with the good side down, and turn the cabinet upside on the top. I move the cabinet as necessary to position it, then use a Vix bit to start the holes for the figure eight screws.

Just have a plan to get the cabinet back on the floor right side up. – lol

-- Adversity doesn't build reveals it.

View lightweightladylefty's profile


3241 posts in 3734 days

#12 posted 02-07-2010 07:05 AM

Sawkerf, now, why didn’t I think of that? (But it is a little tight inside those drawer openings to get much torque on a stubby screwdriver and my right angle drill won’t fit.) When I turned it over before while I was assembling it (it’s actually 6 different cabinets), I used my hoist that’s mounted on the ceiling, but I think it might be overtaxing on it now that the doors are on and once I put the top on it since it’s only rated for about 150 pounds. That’s just another hurdle to jump for this old lightweight!

-- Jesus is the ONLY reason for ANY season.

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